Transparent financial transaction cards and the like can be made with a multilayer interference film whose individual layer thicknesses are tailored to produce a reflection band that reflects infrared (IR) light while transmitting some or all visible light, the multilayer film thus serving as an effective IR filter. Such an IR filter is desirable so that the card, even though it is light-transmissive, can be sensed by IR-based detection systems in automatic teller machines and the like.
FIG. 1 shows an exemplary laminate construction for a financial transaction card 10. In this construction, the card is transparent or translucent and it contains an IR blocking filter 5. The IR blocking filter 5 allows the transparent card to be properly detected by an ATM card reader. Such cards are disclosed in U.S. Pat. No. 6,764,014, titled “Transaction Card”, issued Jul. 20, 2004 (Lasch et al.). The IR filter 5 includes an inner layer of multilayer optical film 50 selected to reflect in the infrared wavelength region and two outer layers 52 (typically polyvinyl chloride or PVC) laminated on either side of the multilayer optical film 50 using adhesive 54. One commercially available form of an IR blocking filter is marketed as Vikuiti™ Clear Card Filter by 3M Company, St. Paul, Minn. In an exemplary card application, the IR blocking filter can be placed in the center of the construction of the card 10, as shown in FIG. 1. The filter 5 including its outer layers 52 can be further laminated with additional outer plastic layers 2, typically PVC, on both sides of the filter 5. A printed layer 4 and optional PVC overlay layers can also be added.